Power Supply Questions

I was thinking of buying a quality 750-850 Power Supply. I already have a 750 watt ZM750 for my current comp, and am looking to buy another for a friend's build.

So far, I've looked at the Zalman 750, Zalman 850, and Corsair 750 (any other recommendations? I want a high quality PSU)

This guy on newegg for the ZM850 PSU review said that a Zalman850 can't power a GTX260 GPU. I think he's BSing...but there are other users who say that the PSU emits screeching noises when high-end GPUs are put in. I currently have a ZM750 and 2x9800GTXs with no problem.

What's the issue here?

Pros: this is a very good power supply. but it is not compatible with gtx 260 or higher video cards, but it is great with 9800 series and lower cards.
if your looking to run dual 9800 gx2's your set. running the nvidia 200 series with one card your not.

Cons: +3.3V@25A,+5V@30A,+12V1@18A,+12V2@18A,+12V3@28A,
+12V4@28A,+12V5@18A,+12V6@18A,-12V@0.8A,+5VSB@3. 5A

looking at the 6 +12v rails, rail 3 and 4 have 28 amps the gtx 260 requires 36 amps. this is not enough for 1 gtx 260 so don't even try 2

Other Thoughts: when buying a psu look at the amps per rail rating, the psu will only put out what is rated on a single rail. the rails do not share amps and each rail is limited to the max for that rail. so look at the sticker on the side of the psu and then make your choice based on the amps rating. the watts is a general rating the will get you in the park for determining which psu is right for you

Is he correct? And what's with the screeching noises that people say comes from the ZM850?

ZM850 review:
http://www.newegg.com/Product/Prod [...] &Keywords=

ZM750: http://www.newegg.com/Product/Prod [...] 6817379006

Message quoted 1 times
Message edited by Bluescreendeath on 05-03-2009 at 06:06:51 AM

------------------------------ i7 920, E5300
GTX260, HD4870, HD4830

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------------------------------ i7 920, E5300
GTX260, HD4870, HD4830
Reply to Bluescreendeath

Well, if it were me, I'd get the TX750/850. Those are excellent quality PSUs and Corsair is great. You really don't have to look at the Zalman. And as it is for your friend, he may not like to go through troubleshooting/RMA if it really doesn't work with a GTX260. And the GTX260 uses less than 12A. Plus I think two PCI-E connectors come from different rails.

No he's talking out of his arse.
The PSU has 60 Amps available to its 12v rails 720W divided by 12. It has 6 rails all rated at 18, there are no 28 Amp rails. Your PSU has 4 20 Amp rails but has the same 720W available or 60 Amps.
Im sure you have realised by now that given the numbers i am posting you cant get all the rails loaded to the max at the same time. This i think is what the reviewer is getting mixed up with.
Also when the reviewer says a 260 requires 36Amps what is probably meant is that the specs require a PSU with 36 Amps. If the card itself needed 36 Amps that would have it using 432 Watts, clearly rubbish.
The ZM850 has all the connectors needed to run two such cards GTX260 and i see no reason why it cant do so.

These are the recommended PSU specs from a review.

GeForce GTX 260 | 280

A GeForce GTX 260 requires you to have a 500 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 38 Amps available on the 12 volts rails.
A GeForce GTX 280 requires you to have a 550 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 40 Amps available on the 12 volts rails.
GeForce GTX 260 | 280 SLI

A second GeForce GTX 260 requires you to have a 700 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 50 Amps available on the 12 volts rails.
A second GeForce GTX 280 requires you to have a 800 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 55 Amps available on the 12 volts rails.

Personal preference would be something from Corsair, say a 750TX which has enough adaptors 4X6+2 and has the same 60 Amps but on a single rail.

Mactronix

Reply to mactronix

I have no clue about the scretching noise.

The best 750-850 PSU that I know of is the Antec Signature series in that range. (there is an 850, not sure about anything lower.) It would cost a ton however, and your better off just getting the Corsair 750. Should be enough to just about power anything buy your hybrid car...

------------------------------ The voice of REASON
Do NOT feed the TROLLS!
Always a DEMON!
Reply to 4745454b

^ thanks. Although what's up with the reviewers talking about the screeching noises for the ZM850?

Also, would a single powerful 60a rail be better than 4 20a rails?

------------------------------ i7 920, E5300
GTX260, HD4870, HD4830
Reply to Bluescreendeath

A single high amperage 12 volt rail is always preferable to multiple 12 volt rails. I personally own the Corsair 750 and highly recommend it.

Reply to jlabit

^ I'm thinking of just getting another Zalman750. It's enough for 2xGTX260s but 2xGTX275s?

*Along with an i7 CPU, which I've heard is power hungry

------------------------------ i7 920, E5300
GTX260, HD4870, HD4830
Reply to Bluescreendeath

Truth is there really isn't a difference between multi rail units and single rail. There is no such thing as trapped power, and there aren't any devices out there that can pull more then 18A. (and if there is, just make sure the second PCIe plug is from a different rail.) I would buy on price, # of plugs, warranty, etc before worrying about whether its a multi rail unit or not.

------------------------------ The voice of REASON
Do NOT feed the TROLLS!
Always a DEMON!
Reply to 4745454b

K, it'll barely be enough for for two GTX275s right? I hope the DX11 cards are more power efficient than the current GTX200 GPUs.

------------------------------ i7 920, E5300
GTX260, HD4870, HD4830
Reply to Bluescreendeath

I wouldn't bet on them being more power efficient (at least not much more).

As for the screeching noise or whatever those reviews said, sounds like it was defective. If you hear that with the one you buy, return it. All products are defective now and then.

------------------------------ New Build (Under Contruction): Intel Core i5 750 > Gigabyte GA-P55-UD4P > 2x2GB GSkill 1600MHz CL7 1.65V > Samsung Spinpoint F3 1TB > Antec 300 Illusion > Asus 4850 512MB w/AM Cooler > Corsair 650HX > Hyper 212 Plus > See other Builds in Member Config
Reply to EXT64

Bluescreendeath wrote :

I was thinking of buying a quality 750-850 Power Supply. I already have a 750 watt ZM750 for my current comp, and am looking to buy another for a friend's build.

So far, I've looked at the Zalman 750, Zalman 850, and Corsair 750 (any other recommendations? I want a high quality PSU)

This guy on newegg for the ZM850 PSU review said that a Zalman850 can't power a GTX260 GPU. I think he's BSing...but there are other users who say that the PSU emits screeching noises when high-end GPUs are put in. I currently have a ZM750 and 2x9800GTXs with no problem.

What's the issue here?

Pros: this is a very good power supply. but it is not compatible with gtx 260 or higher video cards, but it is great with 9800 series and lower cards.
if your looking to run dual 9800 gx2's your set. running the nvidia 200 series with one card your not.

Cons: +3.3V@25A,+5V@30A,+12V1@18A,+12V2@18A,+12V3@28A,
+12V4@28A,+12V5@18A,+12V6@18A,-12V@0.8A,+5VSB@3. 5A

looking at the 6 +12v rails, rail 3 and 4 have 28 amps the gtx 260 requires 36 amps. this is not enough for 1 gtx 260 so don't even try 2

Other Thoughts: when buying a psu look at the amps per rail rating, the psu will only put out what is rated on a single rail. the rails do not share amps and each rail is limited to the max for that rail. so look at the sticker on the side of the psu and then make your choice based on the amps rating. the watts is a general rating the will get you in the park for determining which psu is right for you

Is he correct? And what's with the screeching noises that people say comes from the ZM850?

ZM850 review:
http://www.newegg.com/Product/Prod [...] &Keywords=

ZM750: http://www.newegg.com/Product/Prod [...] 6817379006

I REALLY trust Newegg reviews...

Check out jonnyguru.com for reviews that I DO trust. May not have the exact models you're interested in, but will have enough to give you an indication of that MFG's designs in general.

Also, here's a link to a fairly decent PSU calculator: http://extreme.outervision.com/psucalculator.jsp

Reply to croc

Quote :

it'll barely be enough for for two GTX275s right?

What will? The Corsair or the Antec sig? If the PSU your looking at can SLI the GTX280/285, it will handle the GTX275 just fine. Flying off the seat of my pants, both can probably do it, though you'd be better off with the Antec 850W sig due to the extra 100W. (it has an extra 5A on the 12V rail due to that extra 100W) I have no clue if you want to spend $250 for a PSU however.

http://www.newegg.com/Product/Prod [...] 6817371018

------------------------------ The voice of REASON
Do NOT feed the TROLLS!
Always a DEMON!
Reply to 4745454b

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